Place ½ cup sweetened coconut flakes into a food processor or blender and process until finely chopped. Set aside.

In a medium bowl, whisk together the flour, kosher salt, and chopped coconut. Add the cold butter and shortening, tossing to coat. Using a pastry cutter or fingertips, cut the fats into the flour mixture until it resembles coarse crumbs with some pea-sized pieces remaining. Gradually add ice water, stirring with a fork, just until the dough comes together.

Transfer the dough to a work surface and gently knead until cohesive. Shape into a 6-inch disc, wrap in plastic wrap, and refrigerate for 1 hour.

Roll the chilled dough on a lightly floured surface into a 12-inch circle, approximately ¼-inch thick. Fit into a deep 9-inch pie dish. Trim excess dough, fold edges under, and crimp as desired. Refrigerate for 15 minutes.

Preheat the oven to 375°F (191°C). Line the crust with parchment paper and fill with pie weights or dried beans. Cover the edges with foil. Bake for 20 minutes. Remove weights and parchment, then bake an additional 5 minutes until the crust is set but not browned. Allow to cool slightly.

In a medium bowl, whisk together granulated sugar and melted butter. Add eggs and whisk until smooth. Whisk in buttermilk, vanilla extract, and salt. Stir in coconut flakes until evenly distributed.

Reduce oven temperature to 350°F (177°C). Pour the custard filling into the prepared crust. Bake for 45–55 minutes, or until the custard is set and lightly golden on top. If the crust browns too quickly, loosely cover edges with foil.

Transfer the pie to a cooling rack and allow it to cool completely before slicing. Serve as desired.